This year I have often observed a picture of trees and bushes here like candles “burning” the tops of light shoots in a lush green canopy. This is chlorosis. most of us learned about chlorosis from our school biology classes.
We remember it as iron deficiency… But the truth is that chlorosis is a vague concept. And leaves are not always the cause of iron deficiency.
In this article, we are told what is chlorosis, what iron our plants are deficient in, and how to help them properly.
WHAT IS CHLOROSIS?
Chlorosis is essential – an externally manifested sign that the plant is wilting and its tissues are slowing down the formation of chlorophyll and thus reducing the activity of photosynthesis. This can be a brightening of the leaf layer between the veins along with the veins, leaf margins, leaf spots, or the entire leaf surface, i.e. a change from normal color to light green, yellow, cream.
At the same time, leaves can lose color from petiole to tip, as well as from leaf edge to petiole, starting from the upper, middle, or lower part of the shoot. These additional features are important to observe when determining the problem because it is these and some other features (to be discussed later) that suggest the cause of chlorosis. And there are many causes.
The name “chlorophyll” comes from the Latin word chlorosis, chlorophyll.
TYPES OF CHLOROSIS
Although chlorosis seems to be a generic term, science has classified it into several different types.
- non-infectious chlorosis.
- infectious chlorosis.
- and cerebral dystrophy.
The appearance of each disease is similar, but the causes are different, and therefore the control measures are different.
The most common non-infectious chlorosis is due to the lack of any of the elements in plant nutrition: sulfur, zinc, calcium, potassium, and magnesium. And the most common is carbonate chlorosis (calcareous chlorosis, or iron chlorosis) caused by iron deficiency.
The most common cause of iron chlorosis is too much lime in the soil, which causes an alkaline reaction (pH = 7 or more) that prevents iron from being used by plants. It occurs quite frequently because carbonate soils are quite common.
Symptoms of iron chlorosis appear first on plants in spring or early summer when the leaves on the tips of shoots turn lighter while the veins remain green. This phenomenon is usually triggered by cold and rainy weather, which increases the alkaline reaction of the soil (overwatering and cold soil).
With chronic iron deficiency, young leaves stop growing and older leaves gradually lose their color. If this problem is not solved, the leaf greenery will wither and fall off, and the shoot tips will die.
Other symptoms of iron deficiency are.
- insufficient maturity of wood (reduced frost resistance).
- shedding of fruits.
- growth of short nodes.
Iron chlorosis can also occur in vegetable crops. In tomatoes, mainly on the upper leaves, inflorescences grow small and bushes often die.
In beetroot the old leaves are small and hard, the young leaves are light in color and the tips are scorched; root crops are lignified. In cabbage the old leaves become pale, the young leaves do not grow, the heads are immature and have a bitter taste. In potatoes, old leaves lose their color and appear scorched.
Manganese chloride poisoning
Manganese deficiency can occur in carbonate and acidic calcareous soil. However, when the deficiency is slight, the color of the leaves does not change, and only when the deficiency is severe. Yellowish staining spots of varying shades appear, located between the veins. The plant growth is delayed, while the upper buds do not die.
In addition to trees and shrubs, the so-called indicator vegetable plants also react to the deficiency of this element with chlorosis. Young leaves of cucumber grow light green with yellow edges and scattered spots of necrosis on the leaf plates.
In tomatoes, the mesophyll leaf surface turns yellow from the area away from the central vein, and the discolored area wilts. In potato, the upper leaflet inter-vein lightened, dotted necrotic spots along the wilting tissue scattered.
Magnesium deficiency is obvious on the lower old leaves. Leaf color loss is not uniform, but between the main veins, starting from the leaf margin. Sometimes the color will become red or orange. Necrosis also starts from the same direction as the yellow spot or the middle. These symptoms do not necessarily appear on all branches and even less on all plants.
Other symptoms of magnesium deficiency are.
- weakened plant growth.
- a smaller, less brightly colored fruit.
- early crop maturity.
- lower frost resistance.
In the absence of sulfur, the color of the upper, young leaves changes. First lightens the veins, then lightens the leaf plate tissue. Leaves often turn white with a reddish tinge. Plants stop developing and become more susceptible to water deficiency, diseases, and low temperatures.
In sulfur chlorosis, nitrate accumulates in plant tissues.
Calcium chloride poisoning
Calcium deficiency also causes chlorosis. leaflets turn yellowish-green, stem tips have yellowish-brown spots, and leaf edges are serrated. If calcium deficiency is prolonged, the root system becomes stunted and gradually dies. In a few cases, necrotic ring spots appear on the bark.
Other symptoms of calcium deficiency are.
- crumbling of the fruit with a tendency to crack and tan.
- Earlier ripening of crops.
- Increased susceptibility to vitreous flesh and internal decay – reduced shelf life.
Initially, nitrogen deficiency manifests itself as uniform lightening on the lower older leaves (including the veins and leaf plate tissue). The leaves first take on a light green tint, then a yellowish-green color, and in severe nitrogen deficiency, the entire plant loses its healthy color. The volume of the root system is reduced. Stagnation is observed and the stem growth is stiff and thin.
In chronic deficiency, the leaves are lighter and the upper leaflets are curved at an acute angle relative to the stem. Flowering is early, but the flowers are small and few in number. Often, both color and ovary are broken.
Other symptoms of nitrogen deficiency are.
- Early yellowing or reddening of the leaf apparatus.
- Reddish-brown discoloration of petioles.
- Premature ripening of the crop.
- Fruits are brighter in color, but smaller and less flavorful than the variety should be.
This wilting most often occurs on overly acidic soils or during prolonged spring rains when nitrogen is washed out of the root zone. In the latter case, there is no need to fight the nitrogen deficiency, because when sunny, warm weather arrives, the nitrogen levels return to normal, and the plant recovers.
Another cause could be a prolonged drought that triggers the death of microorganisms that convert nitrogen into a usable form for the plant. In this case, you need to water the plants again and the problem should go away.
Too much nitrogen can lead to zinc deficiency. Yellow, orange, or red spots appear on older leaves. Occurs in spring.
In potassium deficiency, wilting appears on older leaves as spots on the margins and between the veins. The pale leaves often curl upward with the margins. Gradually, marginal necrosis appears. Slow plant growth and dryness of young shoots may be observed.
If potassium deficiency is severe, necrosis may affect the entire leaf. Shoots grow short and thin. Plants become unstable to drought and frost. In addition, the fruit grows small and poorly colored; pits appear on the grapes, followed by berry splitting.
Potassium deficiency can occur in areas with frequent rainfall and in sandy soils.
Infectious chlorosis occurs when plants are infected with NEPO-virus. It is carried by insects. Similar to the aforementioned, it begins to appear in the spring, but already manifests itself as a lightening of the leaves along with the veins, with yellow spots or streaks along the veins. At the same time, short nodes are observed on the shoots and margins on the affected leaves. Once summer arrives, the leaves turn green, but the affected area remains chlorotic.
Unfortunately, viral diseases are not treatable today. The only control measure is to treat the plant prophylactically to prevent insect vectors of the virus.
Atrophic disease arises as a result of adverse external influences: sharp deterioration of weather conditions, rapid changes in soil chemistry, a wide range of temperature variations, too much or too little moisture …… It is also due to the poor rooting of the rootstock on the scion.
PREVENTION AND TREATMENT OF NON-INFECTIOUS CHLOROSIS
Determining the cause of chlorosis cannot be done by considering only the external symptoms. For a more accurate diagnosis, a range of symptoms is needed, including the nature of leaf bleaching, the integrity of new shoot development, the “behavior” of older leaves, yield quality, and an analysis of when and where these manifestations occur in relation to the period of the year, weather conditions, and soil quality.
There are different ways to control non-infectious chlorosis. Here are those that are suitable for any type of.
- improving the air permeability and water permeability of heavy soils.
- mulching to retain moisture in the root zone.
- avoiding the use of manure on carbonate soils, since the decomposition of manure releases carbon dioxide, which dissolves lime and therefore increases the carbonation of the soil
- apply fertilizers containing boron, phosphorus, potassium, iron, manganese, and zinc regularly, if necessary.
- Regular and moderate watering.
- the choice of chlorine-resistant varieties.
In case of iron deficiency, it is recommended to.
- treating the sheet equipment with iron salts.
- foliar feeding with preparations such as chelated iron.
- top dressing with ferrous sulfate under the root.
If magnesium deficiency, use magnesium sulfate, potassium magnesite, white wax, dolomite powder.
From zinc poisoning with zinc sulfate, zinc oxide, and superphosphate with zinc.
Sulfur deficiency can be compensated by compound fertilizer – nitrogen, phosphorus, and potassium plus sulfur, diammonium phosphorus, and potassium plus sulfur.
Nitrogen fertilizers – ammonium nitrate, ammonium sulfate, calcium nitrate, urea – are used to compensate for the lack of nitrogen.
If you cannot determine exactly which element is missing, you can feed your plants with any compound fertilizer that contains all the necessary substances.